Here, the casually stylish style translates to a black crew-neck sweater and navy jeans. You could perhaps get a little creative in the footwear department and polish up this ensemble with casual boots. In winter, when functionality is above all, it can be easy to settle for a less-than-stylish outfit. But this outfit proves that you totally can stay toasty and remain equally stylish in winter. And if we're talking outfit ideas for 20-year-olds, this combination is ideal.